You may have a different audit strategy that you use each time, but let's create a thumb rule for our audits for Amazon product listing services.

Categorize Your Keywords/ASIN into 4 types:

High Converting, Low Cost of Sale

High Converting, High Cost of Sale

Low Converting, Low Cost of Sale

Low Converting, High Cost of Sale

1) High Conversion & Low ACOS mean, these keywords/asins bring the maximum no of orders with good ACOS. So, they have the maximum PPC order share! If we somehow control/isolate those then we can control the major chunk of our PPC sales.

2) High Conversion & High ACOS mean, their spending needs to be controlled (bid/placement optimization) because they are high converting but the issue is the profitability! So, we don't compromise on these keywords rather we slowly optimize these keywords.

3) Low Conversion & Low ACOS mean, these keywords/asins bring very few orders but they are profitable that help us improve the overall ACOS of the PPC! So, what we can do is we should target them in groups that would help us get profitable orders, and once we find a keyword that improves its performance we can shift it to the 1st category.

4) Low Conversion & High ACOS mean, these are the main bleeders that are increasing our ACOS and not giving any good no. of orders. So, we need to make decisions on these keywords/asins thoroughly before making them negative! If the CTR is good enough? Is any particular placement bleeding or every placement is bleeding? Is this keyword/asin working well with other match types/campaign types? If this keyword/asin is relevant enough? Whether you can afford this CPC or Not? Ask several questions before making any kw/asin negative.

If you do your audit around this broad strategy, you can control the ACOS & the profitability with the passage of time.